New question for the sparkers out ther

[Andrew Borgogna]

Well here is an update on my venture into the world of spark ignition.  Last Sunday I put in several flight with the zilch on spark only.  But I am still not getting the kind of power on spark that I get on glow.  All things being equal, same fuel, prop, engine, and plane on glow I can do everything in the old time pattern.  Change just from glow to spark and it flies but not with the authority to do even a good wing over. 

So here are some questions, what is the best points gap setting currently I am just under .008" set with a gauge I made from .008" brass sheet metal.  What is the best setting for the advance, right now I just move the advance lever to full advance.  Below is the answer to the usual questions.
1.  25% Castor 3% syn. x 10% nitro the rest being methanol.
2.  9x6 Master Airscrew wood prop.
3.  MECOA Forster .35
4.  Don Hutchinson electronic spark module.
5.  60' eyelet to eyelet solid lines, Larry Renger can you confirm this.
6.  One of Eric Rules ST NVA (the one sized for the Fox .35) assembly's the original needle was missing and MECOA can't replace it.
7.  Woody Bartlett V2 Spark plug, on the bench I get a beautiful blue spark with each rotation of the prop.

Any help on this will be greatly appreciated, I now have the engine running as well as any of my F/F sparkys but it is just not quite good enough for control line old time stunt.  What ever happens I will fly this plane at VSC even if it is just to go around and around.  I find even going around in circles with this plane to be a real trip, kind of like taking a trip back to the old days.  As Larry said last Sunday "put a glow plug in it and fly Old Time Stunt" maybe, but this is a project to fly ignition and that is still the plan.
Andy

[Andrew Hathaway]

I don't have any knowledge of running a Forster on spark, but have a Forster 35 glow on a Ringmaster.  The part of your setup that stands out to me is the NVA.  The stock Forster spray bar is a very small diameter, like 1/8" or narrower.  Substituting a larger ST NVA would choke down the venturi, costing you power.  Just a thought.

[Jim Kraft]

I would tend to agree with Andrew Hathaway, in that the spray bars are much smaller in the Forster. Having said that, I would think it would run about the same way on both spark and glow on the same fuel, although I have seen some engines that do run different when changing from glow to ign. But in general they seem to run better on spark than on glow. I ran a Forster 29 rear valve in a Dragon for awhile, and it did a fine job on gas oil mix. Your point setting sounds about right at .008", and it is not to critical anyway. The Forsters do like to be run in a wet 2 stroke as they just do not have enough power in a 2-4 break setup. If the engine is well broken in, it should take full advance on the timer just fine. Just for grins you might want to try it on gas/castor mix just to see how that works, but generally they do run better on glow fuel. If you do try gasoline, don't forget to change the fuel line. One other thing you might try is going to a 10-6 prop. These things put out quite a bit of torque on spark.

[De Hill]

Hi Andy,

What diameter are your lines? At Tucson, you will be dealing with 2,00 foot plus altitude, and it will lower the performance of the engine and airplane. Try shortening the lines 2 feet. Be prepared to shorten more at Tucson if you have to. And like Jim Kraft suggested try different propellers. 10-5, 10 -6, and different brands of 10-5 and 10-6 propellers.

Good Luck,

De

PS: Bring spare parts to repair your Ignition system! If it's going to go wrong, it will do it at the VSC. I have seen a lot of frustrated people over the years because they burned out a coil ,or fouled a plug, and didn't have a spare. Rusty Brown showed up at the VSC one year, and found that he had forgotten  his engine!

[Jim Kraft]

What De says is to true. If you have all the parts with you, you will never have any problems. I take a complete ign. system, extra spark plugs, a soldering gun, extra wire, and even some heat shrink tubing. So far all I have had to use was a spare plug as my engine quit inverted in practice, and wiped one out. I am sure that if I did not have all the extra stuff I would have way more trouble. There is one thing on the ign. circle though, and that is if you have any trouble there will be several to jump in and help. Great bunch of guys, and a whole lot of fun.

De; Are you going to fly ign. this year since you are not running the event? You need to get in on the fun side of the ign. event. We will have fun.

[De Hill]

Hi Jim,

Yes; Charley Bruce wants me to fly his Foxy in Ignition. It's the Red one with a Fox .59 longshaft in it.

De

[Andrew Borgogna]

Thanks guys for the info, I will look through my stash of NVAs and see if I have one with a narrower spray bar.  I have given some thought to trying different props, I got a 10x5 but it wound up at Larry Renger's.  We were going flying this weekend but it looks like the rains of 2008 are going to continue.  As far as spare parts, I have a complete set of plugs, electronic module, coil and high tention wire.  I will bring them all along with solder and a iron and some shrink tubing.  I won't be able to use gas in my current setup, the tank is brass with a clunk using silicon tubing.  I plan to build a new tank after VSC, but for the time being I am committed to glow fuel.  I think I will have Eric Rule cut be a set of 52' solid lines and take them to VSC.  Glad to hear there will be plenty of help if I need it, regardless of the outcome I am having a ball playing with spark.

De just a note to let you know I got the motor and I am quite happy with it.
Andy

[Jim Kraft]

Alright!! Sounds great De. Looking forward to it. I think I am going to fly my new Humongous with a Spitfire this year. I got about 50 flights on it before the weather got bad, and it is coming along nicely. I will probably throw in the Taurus also for a backup plane. It is easy to transport since it is a takeapart. I'm really glad you are flying this year.

[Larry Renger]

As I recall, Andy's lines are 57' x .012 solids.  On glow, the plane flies remarkably well.  I see no reason why ignition, which is a really accurate way to initiate combustion should run worse than the hit or miss of a glow plug triggering the fire at some compression/mixture level. 

Andy also seems to have a sag-off at the end of the flight on ignition that makes me think overheating, thus too much advance.  My guess is that excess advance should look the same as over-compression, too hot a plug, too large a prop or excess nitro on a glow engine. 

So, to my way of thinking, if I were designing an ignition system, I would allow a slight excess of advance to be possible to assure that there will be enough available for optimum setting.  With that said, I expect that full advance is normally too much.

This raises the question of how do you set the advance to optimum?  On a diesel, you NEVER go for maximum compression, excess is ALWAYS available (and lethal!).  Learning how to tune the engine is part of the equation.  On glow, you adjust head gaskets, prop, nitro content and plug heat.  On a diesel you set the compression and needle, and occasionally ether content.  What is the optimum plan for ignition???

Admittedly, I have never run an ignition engine, but I propose that retarding the spark until a slight rpm drop happens may be the way to go.  Comments?

[Alan Hahn]

edited to clarify some of my remarks!!

Since all you do is to change from a glow plug to a spark plug and in the process lose power, I don't think it is the spraybar. Of course a narrower spraybar might give more power in both glow and spark cases.

So when you adjust the advance, do you adjust for max rpms? And if you do I assume it is lower than the rpm you get just before launch with the glowplug(or not?).

One thought is whether you have the same compression when you replace the glow plug with the sparkplug, You might be losing if there is more air spacevolume in the spark plug body.

Otherwise I am wondering if you are getting as efficient a combustion. What is happening to the needle? Is it left the same or do you have to lean or richen it. If it were a simple plug replacement and everything else was equal, the needle would stay the same--I would think.

I have no answers (obviously! ), but maybe you can figure out what is changing besides just the plug.

[john e. holliday]

After my little jaunt into Ignition and talking with Lew Wollard, we figured out I did not have enough prop on the little O&R 23.  I was trying a Top Flite 9-5.  He stated he usually runs a bigger prop than recommended diameter wise.  You might try more diameter and let us know.  DOC Holliday

[Charlie Pate]

 Just a thought,
Have you tried taching it on the ground and varying props and timing (advance lever) and comparing
Rpms against your glow.
The engine is heavily loaded sitting on the ground. Very.

[don Burke]

Andy,
"Thanks guys for the info, I will look through my stash of NVAs and see if I have one with a narrower spray bar."
If push comes to shove a file applied to the sides of the spraybar will cut down it's width which is what matters when restricting the venturi.  The upper and lower edges left can be slightly radiused for smoother flow.  I have filed a Fox 35 with ST NVA down to .117 wide for FOX racing.  Worked OK, and it doesn't lower the strength of the bar like turning it down would do.

[Andrew Borgogna]

Thanks to all for your input.  Doc, I definitely intend to go to a larger diameter prop (Oh Larry did you find the 11x5?).  I think the idea of tacking the engine with a good glow setting and then play with the variables on spark to try to achieve the same rpm/prop combination is a good way to get a base line for the engine.  Yesterday I contacted Eric Rule at RSM and he is cutting me a set of .012" solid lines at 52'.  Currently I am using 10% nitro and fly near sea level, when I go to VSC I plan to move up to 15% to compensate for the altitude.  Some one pointed out that if it runs right with glow the NVA may not be the issue, makes sense to me.  The Forster .35 run quite well on glow certainly equal to a McCoy or Fox of the same displacement.  In fact Larry has suggested I put a glow plug in it and enter OTS in addition to ignition.  I am giving this serious thought, it may get a bit hectic trying to fly in all three events but heck VSC is only once a year.  What I lack in skill I will make up in volume.

Lord do I enjoy this hobby!
Andy

[Andrew Hathaway]

Does nitro do anything for the engine when running on ignition?  I've only run my spark engines on the bench, but they don't seem to be effected by nitro.  In fact the fuel I've been burning up on ignition is some stuff I've had around for years that won't even fire with a glowplug. 

[Larry Renger]

Gasolene has more BTUs per ounce than Methanol, but if I remember correctly, the fuel/air mix possible with methanol compared to that of gas allows you to pump more power out of the engine.  WAY worse gas mileage, of course.

I understand that if you have continuous electrical power to a glow-plug you can run a gas/oil mix or even model diesel fuel in a glow engine.    Certainly with modern batteries it is no problem to keep the plug lit for 8 minutes with minimal battery weight, and you will probably save more weight than that in fuel load.  Anyone out there experienced in this technique?

The RC boys use on-board packs to assure reliable idle on some of the large models.

[Jim Kraft]

I've run sparkers on the bench on gasoline with a glow plug just to clear a flooded engine. My experience has been that they don't run to well that way. It does do the job of cleaning out the flood though. The glow plugs, once the engine is running, do not draw much current, as the element becomes high resistant as it is heated. I have never tried running with a battery attached, but I did read an article a few years ago about doing this very thing. Can not remember much about it though, and this was for running on glow fuel.

[Andrew Borgogna]

gasoline vs. methanol.  Gas burns at approximately 16x1 air to gas ration.  Methanol burns 6x1 air to methanol ration.  Yes gas per given volume has more BTU (British Thermal Units) of energy, but (and it is a big but) you can burn approximately 2.5 times as much methanol before the mixture becomes too rich to burn.  Then if you add Nitro, which is an oxidizer you can burn even more.  So all things equal methanol/nitro combination will give more overall power but at the cost of mileage.
Andy

[Larry Renger]

Thanks, Andy, for bailing me out.  I knew the essentials, but was too lazy to look up the specifics.  I blush to admit that I sort of remember general guidelines, and then work with them, but don't have the patience to get too detailed.  So far, I have gotten away with it.  Fortunately, I know a LOT of guide lines....